The invention relates to apparatus for supplying gas to a fluidisation grid having at least two separate circuits, each having multiple outlet orifices.
A grid of this type can be employed, for example, in a combustion hearth for a granular fuel of the type described in French Pat. No. FR-A-82/00,815. In this grid, a first circuit for injecting air, which is fluidising air, ends in a large number of orifices situated in a first plane of the grid, and a second circuit for injecting air ends in a large number of orifices situated preferably in a second plane of the grid, placed at a level above the level of the first plane. For example, the orifices of the second circuit are at different levels relative to pyramidal frusta which stand alternately starting at the surface of the grid.
The advantage of such a grid is that it makes it possible to regulate the rate of combustion and the hearth power over a wide range by adjustment of the flow of air through each circuit. It is desirable to control the respective flow in each circuit and, also, to control the flow injected through some orifices in relation to other orifices belonging to the same circuit, and thus heretofore a large number of flow-control diaphragms and valves have had to be employed, the management of which becomes a real problem.